The importance of mineral nutrition may be one of the most unrecognized factors contributing to grazing cattle performance. Forages and grains, the common feedstuffs fed to cattle, are nutritionally incomplete. The extent to which nutrients are lacking depend on feedstuff quality and cattle nutrient needs. Forages, the foundation of grazing cattle diets, rarely, if ever, provide all the minerals required by grazing cattle. The nutritional content of feedstuffs can vary tremendously depending upon:

• Soil type

• Weather conditions

• Time of year

• Fertilization levels

• Stage of maturity

• Storage conditions

Overtime, soils can also become depleted in mineral content, resulting in lower mineral levels in forages; hence, the need to provide supplemental minerals and vitamins.

Need
While minerals comprise only a fraction of the total amount of nutrients required by cattle, they form the nutritional foundation needed for productive cattle programs. Minerals are needed for normal tissue growth, enzyme function, cell regulation, homeostasis, and immune function. Table 1 lists minerals and vitamins required by cattle.
 

Table 1 Minerals and Vitamins Needed by Cattle
Macro Minerals	Micro Minerals	Vitamins
Calcium Phosphorus Magnesium Salt Potassium Sulfur	Copper Zinc Manganese Cobalt Iodine Iron Selenium	Vitamin A Vitamin D Vitamin E Typically, ruminants are not supplemented with B vitamins because they are produced in the rumen.

Overall animal performance can be negatively affected when the diet lacks sufficient quantities or mineral ratios are incorrect. Inadequate dietary intake of minerals has been associated with the following:

• Reduced forage intake

• Lower reproductive efficiency

• Lower gains

• Poorer feed efficiency

• Lower disease resistance

Unrecognized mineral status insufficiency (subclinical deficiency) is difficult to detect. Figure 1 (click to enlarge) depicts the effects of trace mineral deficiencies in cows and calves. A mineral deficiency first impacts the immune system. Subtle effects on immunity often go undetected. Slow growth rate and/or poor reproductive performance may also be a result of insufficient mineral intake. Because health challenges and poor performance can be influenced by many factors, the mineral status of a herd may often be overlooked.

Efficiency of production continues to be lost when mineral insufficiency goes uncorrected. Mineral deficiency manifested by clinical symptoms is usually critical. The most commonly recognized mineral deficiency is hypomagnesium, which effects cattle grazing low magnesium forage (such as stockers on wheat pasture). Most mineral insufficiencies are typically subclinical, meaning producers won’t see obvious signs. What occurs is production on a level below what could be obtained with optimum mineral nutrition.

Value
The investment in a sound mineral program can reap dividends in terms of:

• Immune system function

• Reproduction

• Forage digestibility

• Feed efficiency

• Body weight gain – body condition score of brood cows and growth of calves, replacements, and stockers

Research has shown cattle provided trace mineral supplementation have a positive response to immune status (measured by an increase in cell mediated immunity). Cattle with healthy immune systems are better able to handle stress and infectious challenges. And simply, healthy cattle are more productive.

The impact of phosphorus supplementation on reproductive performance has been documented in numerous research trials (Table 2). Pregnancy rate and calf weaning weight responded positively to phosphorus supplementation. In a three-year USDA trial, calcium and phosphorus supplementation of cattle grazing native range responded with increases in conception rate, milk production, and weaning weight (Table 3). Trace minerals are also important to reproduction as evidenced in Table 4.
 

Table 2 Effect of Phosphorus Supplementation Versus Control
		Improvement over Control
Class of Cattle	Phosphorus/day, g	Pregnancy rate, %	Calf Weaning Weight, lb
Brood cow	2.3	0	14.3
Brood cow	4-8	2.7	17.4
Heifer	4-6	7.0	18.7
Sources: J. Range Manage. 50:2-9 (1997); J. Prod. Agric. 5:409-413 (1992); J. Range Manage. 48:493-497 (1995); J. Range Manage. 53:170-175 (2000).

 

Table 3 Effect of Calcium and Phosphorus Supplementation on Cow/Calf Performance (native range)
	Performance Advantage over Controls
Conception rate	6%
Milk production	17%
Weaning weight	16 lb
Three-year average cow performance, USDA, North Dakota (1984).

 

Table 4 Effect of Supplemental Trace Minerals on Conception
	Control	Supplemented with Manganese, Copper, and Zinc
Days to first estrus	60	61
Days to conception*	32	21
Services per conception	1.7	1.2
Cows pregnant on first service	40%	84%
Conception rate at end of trial	83.3%	95.0%
*Interval in days between start of breeding season and conception. Source: J.C. Meiske, University of Minnesota

Economically, a 16 lb weaning weight advantage could provide an extra $19.20 per calf based on a weaned calf value of $120/cwt. Fewer days to conception and better conception rates also provide an economic incentive for mineral supplementation.

Rumen Perk
One of the major benefits of mineral supplementation is the positive effect on the rumen microbial population. Simply feeding the tiny microorganisms in the rumen with the correct amounts and proportions of minerals has a dramatic impact on production. Rumen microbes utilize calcium, phosphorus, magnesium, potassium, iron, manganese, cobalt, copper, molybdenum, and sulfur for non-protein (like urea and biuret) utilization, protein synthesis, fiber digestion, carbohydrate fermentation, and energy utilization.

Nutrient supplementation has a positive effect on the number and activity of rumen microbes as shown in Figure 2. As the microbial population increases due to proper mineral supplementation, so does forage digestion, which enables the animal to consume more forage. The end result is more energy is available for production purposes from the same amount of forage – that’s economy plus production!

Just Salt

Salt or trace mineralized salt will not meet all the mineral needs of cattle. For optimum forage digestion and cattle performance, cattle need a balanced macro and trace mineral program in addition to vitamins. Figure 3 shows the difference in nutrient digestion in cattle fed just salt compared to a balanced mineral program. This University of Missouri study documented the effects of salt versus mineral supplementation for steers consuming Sudan grass hay (Figure 3). The digestibility of fiber, protein, and TDN was greater for steers fed mineral versus those fed salt. Steers consuming the mineral were able to extract more nutrients from the forage, which can reduce cost of production and also enable better performance. The average daily gain of steers fed mineral was 0.2 lb/head/day more than salt-fed steers.

Yes
Providing a properly balanced mineral enables grazing cattle to obtain more of their needed nutrients from the forages consumed rather than getting needed nutrients from grains or additional supplements. Feeding a balanced mineral program can reduce total cost of production by increasing forage digestion, which in turn can increase performance. A balanced mineral program can also have positive effects on reproductive performance and immune system function.